Web drying apparatus



July 9, 1957 A. sUNNEN, JR

WEB 'DRYING APPARATUS Filed Dec. 4, 1955 ATTORNEY United Sttes atent WEB DRYING APPARATUS August Sunnen, Jr., Nashville, Tenn., assigner to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application December 4, 1953, Serial No. 396,294

Claims. (Cl. 3456) This invention relates to web width control mechanism, and, more particularly, to a device for automatically controlling the width of continuous regenerated cellulose film in the dryer of the casting machine.

The dryer of a typical regenerated cellulose casting machine consists of two horizontal banks of heated rolls. The wet gel regenerated cellulose film passes alternately over the top of an upper roll, then under the next lower roll, etc., until the end of the dryer is reached, where the dried film is wound up. In the manufacture of regenerated cellulose lm, it is desirable that the Ywidth of the film winding up remain constant. It is well known Ythat the width varies from time to time for various reasons. It is also well known that the lm width can be changed by threading out a lower roll of the series of spaced rolls which constitute the dryer of the conventional casting machine. When a lower roll is threaded out (skipped), this gives an untentered section of lm equal to the distance between the center lines on adjacent upper rolls. A shrinkage in width 1/2" to is usually obtained with such a skip. However, it is necessary to break the film in order to thread a roll in or out, causing a delay in time and a waste of ilm. Then too, the amount of width change caused by threading in or out is not always predictable.

The principal lobjective of this invention, therefore, is to provide an apparatus for automatically controlling the width of regenerated cellulose film in the dryer whereby it is not necessary to break the lm'in order to compensate for width changes caused by process Variables. Other objects will appear hereinafter.

These objects are realized by the present invention which, briey stated, comprises means for raising and lowering a dryer roll adjacent the wet end of the dryer, said means being responsive to deviations in the width of the regenerated cellulose lm being dried as it passes a point adjacent the dry end of the dryer.

The apparatus of this invention, in a preferred embodiment thereof, will now be described with reference to the accompanying drawings wherein:

Figure 1 is a diagrammatic view of the dryer section of a conventional casting machine which dryer incorporates the apparatus of the present invention;

Figure 2 is a front view of a preferred mechanism for raising and lowering the dryer roll; and

Figure 3 is a wiring diagram illustrative of one method of controlling a reversible motor responsive to the operation of a web width gauging device.

Referring to Figure l, gel regenerated cellulose film F passes from the conventional softener tank A of the casting machine to the conventional dryer section D, which is comprised of a series of alternating upper and lower rolls, over which the film is passed. In the dryer, some or all of the rolls are heated to expedite drying of the film; and some or all of the rolls are driven, usually by a slipdrive arrangement, to advance the film to the wind-up, where it is collected as a mill roll B. In accordance with the present invention, one of the rolls, e. g., an upper roll ICC 1, near the -wet end of the dryer, i. e., near the end of the dryer adjacent the softener bath, is equipped with mechanism for raising and lowering the roll which, in one embodiment, shown in Figure 2, comprises a roll 1 rotatable on shaft 2 which in turn is supported at each end in, and carried by roll support nuts 3 and 4, engaging jack screws 5 and 6 respectively, the latter Vbeing seated in lower thrust bearings 7 and 8 respectively, and upper collar bearings 9 and 10 respectively, suitably affixed to the frame of the dryer. Bevel gears 11 and 12 are keyed or otherwise fastened to the jack screws 5 and 6 respectively at the upper ends thereof and are in engagement with bevel gears 13 and 14, xedly mounted on shaft 15 driven by reversible motor 16. It will be evident from the foregoing that, depending on the direction of rotation of the shaft 15, as determined by the width signal transmitted to the motor 16, the roll 1 maybe raised or lowered at will, within predetermined limits, with a corresponding increase or decrease in the untentered length of the film passing thereover, and a consequent decrease or increase in the lm width. Any device, indicated generally by the reference numeral 17 in Figure l, that will provide an electrical signal in accordance with a change in the width of the lm at a given pointy in its travel through the dryer may be used in combination with the mechanism just described. Thus, the web width measuring device described and claimed in the copending United States application Serial No. 347,210, filed April 7, 1953 (Roy W. Nash), may be used to generate suitable width signals to be transmitted to and control the operation of reversible motor 16. Briefly, the web width measuring device of the copending application comprises a scanning means located adjacent each running edge of the traveling film, pneumatic shifting means responsive to a lateral (width) shift of the running edge of the film for independently moving each scanning means to follow the lateral shift of the running edge of the lm, and an indicator means including an indicator arm for registering the differential movement of the scanning means; movement of the arm in one direction from a predetermined reference point indicating a decreasing width; and movement in the opposite direction indicating an increase in the width of the lilm. Such a device is conveniently located, as shown in Figure l, to scan the lm at the wind-up end of the casting film at which point the film is substantially dry and is of fixed width. Any deviation from a predetermined setting of the scanning means causes the indicator arm to move to one side or the other. Limit switches 18 and 19 (Figure 3) are located in such position that normally open limit switch 18 is closed by movement of the indicator arm responsive to an increase in the film width from the predetermined reference point; and motor 16 is caused to run in a direction effective to raise roll 1 and thus increase the untentered lm length of the wet or gel film with a consequent decrease in the width of the film. Similarly, normally open limit switch 19 is located to be closed by movement of the indicator arm responsive to a decrease in the width of the film from the predetermined reference point, whereby motor 16 is caused to rotate in the reverse direction to lower the roll 1 and decrease the untentered film length of the wet film. Switches 20 and 21 are provided to insure stoppage of the motor 16 when the roll reaches the limits of its travel. Thus, switch 20 is normally closed and is opened by suitably arranged contact with roll 1 to break the motor circuit when the roll reaches the limit of its travel up; and normally closed switch 21 is opened by contact with the roll at its downward limit of travel. It is to be understood that any other web width measuring device, either electrical, and/ or optical, and/ or mechanical, may be employed in like fashion to actuate limit switches and control the operation of the roll-raising and lowering mechanism. A suitable optical-elecring of the iilrn isnegligible-and the film qualityrisnot adversely'aifecte'd. The film does not have to be'broken `and an innite number of-small width corrections can be made. The amount the roll can'be raised isrlimited only by the construction of a dryer and design of the raising and lowering mechanism. Raising the roll 12" normally causes a width shrinkage of about l to 1%.

It is readily understood that more than one roll may be Vused to'increase the Width'control range of this invention,

and the roll `orrolls'used may be either upper or lower rolls. Moreover, where more than one roll is used, the rolls may be moved simultaneously, or each roll may be moved independently, for example, in sequence.

" For optimum` results, .the roll 'or rolls used should be located in the dryer where the nlm-contains approximately 75-125% moisture. An on-oir` timer may be incorporated in the set-up to allowy time for width changes made in the dryer to be reflected at the width measuring del vice at the wind-up.

Regenerated cellulose iilm made in the usual manner may show width variations as much as 1A" to 3A within a mill roll. On the other hand, regenerated cellulose iilm made with this invention can be produced to a width variation of ils or less of a set point. This permits making the film with less allowance for trim waste when it is slit into narrow rolls. Increased slitting machine production also results since trim breaks due to lm narrowing below limits are eliminated. Unit weight of the lm is also more uniform, since, for a given setting of the viscose pump, unit weight should remain constant with width being held constant.

I claim:

1. In a web dryer comprising a web inlet end, a web outlet end, and a plurality of dryer rolls serially disposed between said web inlet and outlet ends, the improvement which comprises in combination gauging means for continuously gauging the width of the web in said dryer adjacent said web outlet end, and means responsive to the action of said gauging means for positively raising and lowering at least one dryer roll adjacent said web inlet end.

2. In a regenerated cellulose film casting machine dryer comprising a wet end at which continuous gel film is introduced into the dryer, and a dry end from which film after being dried is withdrawn therefrom, said dryer further comprising a series of upper and lower dryer rolls alternately arranged in two horizontal banks extending 4 from said wet end to said dry end, the continuous ilm passing alternately over an upper roll and thence under the next adjacent roll andso through the dryer, the improvement which comprises, in combination, means for raising and lowering at least one of said dryer rolls adjacent said wet end, gauging means adjacent said dry end for continuously gauging the width of iilm in said dryer, adjacent the dry end thereof, and means responsive to the action of said gauging means for actuating said means for raising and lowering at least one of said dryer rolls.

3. The apparatus of claim 2 wherein said means for actuating said means for raising and lowering at least one of said dryer rolls comprises a reversible electric motor responsive to the action of said gauging means.

4. In a regenerated cellulose fllm casting machine dryer comprising a wet end at which continuous gel film is introduced into the dryer, and a dry end from which film after being dried is withdrawn therefrom, said dryer further comprising a series of upper and lower dryer rolls alternately arranged in two horizontal banks extending from said wet end to said dry end, the continuous lm Vpassing alternately over an upper roll and thence under the next adjacent roll and so through the dryer, the improvement which comprises, in combination, means for raising and lowering an upper dryer roll adjacent said wet end, gauging means adjacent said dry end for continuously gauging the width of iilm in said dryer, adjacent the dry end thereof, and means responsive to the action of said gauging means for actuating said means for raising and lowering said upper dryer roll.

5. The apparatus of claim 4 wherein said means for actuating said means for raising aand lowering said upper dryer roll comprises a reversible electric motor responsive to the action of said gauging means for lowering said upper dryer roll when the film at said gauging means decreases in width from a predetermined width, and for raising said upper dryer roll when said ilm increases in width from a predetermined width.

References Cited in the tile of this patent UNITED STATES PATENTS 829,686 Barber Aug. 28, 1906 1,787,520 Hampel Ian. 6, 1931 1,973,245 Bleibler Sept. 11, 1934 1,976,438 Dietrich Oct. 9, 1934 2,565,570 Messinger Aug. 28, 1951 FOREIGN PATENTS 33,515 Norway Nov. 7, 1921 352,086 Germany Apr. 24, 1922 ww -An 

